title: Enhanced surveillance of norovirus outbreaks of gastroenteritis in Georgia.
abstract: OBJECTIVE
  The role of noroviruses in both foodborne and person-to-person outbreaks of acute gastroenteritis (AGE) has been difficult to determine in the U.S. because of lack of routine norovirus testing and of national reporting of person-to-person outbreaks. We conducted a prospective study in one state in which enhanced testing for noroviruses was performed to better understand the relative contribution of all gastroenteric pathogens.
  
  
  METHODS
  During the two-year period, 2000-2001, we took all fecal specimens from AGE outbreaks reported in Georgia that were negative for bacteria and tested these for norovirus.
  
  
  RESULTS
  We investigated 78 AGE outbreaks, from which suitable fecal samples were collected from 57 of them. Norovirus was identified in 25 (44%) outbreaks, bacteria in 20 (35%) outbreaks, and parasites in one (2%) outbreak. Forty-three (75%) of the outbreaks tested were foodborne, of which 17 (40%) were attributable to norovirus and 18 (42%) were attributable to bacteria. Adjusting for incomplete testing, we estimated that 53% of all AGE outbreaks were attributable to norovirus. A total of 2,674 people were reported ill in the 57 outbreaks, and norovirus infections accounted for 1,735 (65%) of these cases. Norovirus outbreaks tended to be larger than bacterial outbreaks, with a median number of 30 vs. 16 cases per outbreak, respectively (p = 0.057).
  
  
  CONCLUSIONS
  This study provides further evidence that noroviruses are, overall, the most common cause of AGE outbreaks in the U.S. Improved specimen collection, reporting person-to-person outbreaks, and access to molecular assays are needed to further understand the role of these viruses and methods for their prevention.
authors.affiliation: National Center for Immunizations and Respiratory Disease, Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. mwiddowson@cdc.gov
authors.forename: Marc-Alain
authors.initials: MA
authors.lastname: Widdowson
authors.forename: Sandra N
authors.initials: SN
authors.lastname: Bulens
authors.forename: R Suzanne
authors.initials: RS
authors.lastname: Beard
authors.forename: Kimberley M
authors.initials: KM
authors.lastname: Lane
authors.forename: Stephen S
authors.initials: SS
authors.lastname: Monroe
authors.forename: Susan
authors.initials: S
authors.lastname: Lance
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Bresee
authors.forename: Roger I
authors.initials: RI
authors.lastname: Glass
mesh_terms: D017250:Caliciviridae Infections / Q000453:epidemiology* / Q000635:transmission; D005243:Feces / Q000382:microbiology / Q000821:virology*; D005759:Gastroenteritis / Q000453:epidemiology* / Q000382:microbiology / Q000821:virology*; D005845:Georgia / Q000453:epidemiology; D006801:Humans; D029322:Norovirus; D011446:Prospective Studies; D018571:Sentinel Surveillance